JP5656842B2 - Rare earth regenerator material particles, rare earth regenerator material particles, refrigerator using the same, measuring device, and method for producing the same - Google Patents

Description

  The present invention relates to a regenerator material particle, a regenerator material group, in particular, a rare earth regenerator material, a refrigerator using the regenerator material, a measuring device, and a manufacturing method thereof.

  In superconducting technology used in magnetic levitation trains and nuclear magnetic resonance tomography diagnostic devices, cryogenic technology has been developed in a wide range of fields such as cryopumps used in ultrahigh vacuum devices such as ultra LSI pattern transfer devices, and their practical use. As we enter the age of development, the development and commercialization of smaller and higher performance refrigerators are being promoted. In particular, the importance of refrigeration / cooling technology that creates an environment near absolute zero (-273 ° C) in which a superconducting magnet or a cryopump for forming a high vacuum in a semiconductor manufacturing apparatus operates is increasing, and high reliability and excellent There is a need for a refrigeration apparatus having characteristics.

  2. Description of the Related Art Conventionally, in a superconducting MRI (nuclear magnetic resonance imaging) apparatus (image measuring apparatus) that takes tomographic photographs in the medical field, for example, a small helium refrigerator (GM refrigerator) of the Gifford-McMahon type is used to cool the superconducting magnet. Is adopted.

  This GM refrigerator is configured by combining a compressor that compresses He gas, an expansion unit that expands the compressed He gas, and a cold storage unit that maintains the cooling state of the He gas cooled by the expansion unit. Yes. Then, the He gas compressed by the compressor at a cycle of about 60 times per minute is expanded by the refrigerator and cooled, and the system to be cooled is cooled through the tip of the expansion portion of the refrigerator. In recent years, pulse tube refrigerators have also been developed. The pulse tube refrigerator is a type of refrigerator that supplies high-pressure He gas to the refrigerator at a predetermined cycle. Since the pulse tube refrigerator has less vibration than the GM refrigerator, it is possible to suppress the generation of noise during measurement by an MRI apparatus or the like.

  The regenerator is filled with a regenerator in any refrigerator. As the regenerator material for refrigerators used in the vicinity of absolute zero, for example, in an extremely low temperature region of 10K or less, further 4K or less, the rare earth regenerator material disclosed in Japanese Patent No. 2609747 (Patent Document 1) is effective. Patent Document 1 enables high-density filling of the regenerator particles by adjusting the particle size and aspect ratio of the rare earth regenerator particles.

  On the other hand, in order to improve the performance of a refrigerator, making a cold storage part multistage type is examined. For example, Japanese Patent Laid-Open No. 2001-272126 (Patent Document 2) discloses a two-stage pulse tube refrigerator. By using multiple stages, the cooling rate can be increased. Further, since the cooling amount can be increased, it can be used for a large apparatus. By using a multistage system, it is necessary to increase the supply amount and supply pressure of He gas.

  The refrigeration performance of the refrigerator is determined by how much He gas can be brought into contact with the surface of the regenerator particles. Conventional cold storage material particles use round particles in order to realize high density filling, and it is difficult to perform high density filling beyond this. If the small regenerator particles are excessively filled in the gaps between the regenerator particles, the air permeability of He gas, which is a refrigerant, deteriorates. In addition, it is conceivable to perform filling while applying a strong pressure. However, if an excessively strong pressure is used for filling, the cold storage material is crushed, which causes clogging. For this reason, the cold storage material which can maintain a high-density filling and can improve a contact surface area with He gas was calculated | required.

Japanese Patent No. 2609747 JP 2001-272126 A

  An object of the present invention is to solve the above-described problems, and to provide a rare earth regenerator material particle having a large contact surface area with a working medium gas such as He gas while maintaining high-density filling. To do. Another object of the present invention is to provide a production method capable of efficiently producing rare earth regenerator particles having a large contact specific surface area.

In the rare earth regenerator particle group of the present invention, in the rare earth regenerator particle group having an average particle size of 0.01 to 3 mm, the ratio of the number of particles having a major axis to minor axis ratio of 2 or less is 90% or more, Ri der number proportion of particles recess having a length in the circumferential length of 1 / 10-1 / 2 on the particle surface is formed is 30% or more, less than 1/10 the depth of the recess is the particle diameter It is characterized by being.

Moreover, it is preferable that the depth of the said recessed part is 1/10 or less of a particle diameter. The rare earth regenerator particles are preferably at least one selected from Nd, Er ₃ Ni, and HoCu ₂ .

Further, the rare earth regenerator material particle of the present invention is a rare earth regenerator material particle having a particle size of 0.01 to 3 mm, the ratio of the major axis to the minor axis is 2 or less, and 1/10 to the circumferential length on the particle surface. A recess having a length of 1/2 is formed, and the depth of the recess is 1/10 or less of the diameter of the rare earth regenerator material particle .

Such a rare earth regenerator particle group is suitably used for a refrigerator equipped with a regenerator container filled with the rare earth regenerator particle group. Moreover, it is preferable that the said cool storage container comprises the cool storage material filling area | region of two or more steps through a mesh material.

  Moreover, it is used suitably for the measuring apparatus provided with the superconducting magnet which mounts such a refrigerator. Moreover, it is preferable that the measuring apparatus is at least one of MRI imaging (magnetic resonance imaging apparatus) and NMR (nuclear magnetic resonance analysis measuring apparatus).

  The first method for producing a rare earth regenerator material particle group of the present invention includes a step of preparing a molten metal containing a rare earth element, and a rotational speed of the molten metal in a chamber in an argon atmosphere of 7000 to 11000 rpm. A step of supplying to the rotating disk; and a step of rapidly cooling the granular metal melt struck by the rotating disk. Moreover, it is preferable to supply a molten metal from the injection nozzle whose diameter is 0.05-2 mm. The rotating disk is preferably made of ceramics. In addition, it is preferable to inject the molten metal after preheating the rotating disk to 800 ° C. or higher.

  The second method for producing a rare earth regenerator particle group of the present invention includes a step of preparing a molten metal containing a rare earth element, and a rotation speed of the molten metal within a chamber in an argon atmosphere at a rotational speed of 7000 to 11000 rpm. A step of spraying from the nozzle, and a step of rapidly cooling the molten metal sprayed from the rotating nozzle. Moreover, it is preferable to supply a molten metal from the injection nozzle whose diameter is 0.05-2 mm. Moreover, it is preferable to inject the molten metal after preheating the rotating nozzle to 800 ° C. or higher.

  According to the rare earth regenerator particle group of the present invention, it is possible to provide a rare earth regenerator particle having an increased contact surface area between a working medium gas such as He gas and the regenerator particle group while maintaining high-density filling. Can do. For this reason, the characteristic of the refrigerator using the said cool storage material particle group, and also the measuring apparatus using the refrigerator can be improved.

  Moreover, according to the method for producing the rare earth regenerator material particle group of the present invention, the rare earth regenerator material particle group of the present invention can be efficiently produced. Moreover, if the rare earth regenerator material particle of this invention is used, a rare earth regenerator particle group can be comprised efficiently.

FIG. 1A is a perspective view showing an example of a rare earth regenerator material particle according to the present invention, and FIG. 1B is an enlarged cross-sectional view taken along line BB in FIG. 1A. It is a perspective view which shows the other Example of the rare earth cool storage material particle | grains which concern on this invention. It is a perspective sectional view showing one example of a manufacturing method of rare earth storage material particles concerning the present invention. It is a perspective sectional view showing other examples of a manufacturing method of rare earth cold storage material particles concerning the present invention. It is sectional drawing which shows the example of 1 structure of GM refrigerator.

  The rare earth regenerator particle group of the present invention is a rare earth regenerator particle group having an average particle size of 0.01 to 3 mm, the ratio of the number of particles having a major axis to minor axis ratio of 2 or less is 90% or more, The number ratio of the particles in which the concave portions having a length of 1/10 to 1/2 of the circumferential length are formed on the surface is 30% or more.

  First, the rare earth regenerator material contains a rare earth element as a constituent element. As rare earth elements, Y (yttrium), La (lanthanum), cerium (Ce), praseodymium (Pr), niobium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), Examples thereof include at least one element selected from terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb).

In addition, rare earth regenerator materials include rare earth elements alone, alloys with Cu (including intermetallic compounds), alloys with Ni (including intermetallic compounds), rare earth oxides (including rare earth composite oxides), and rare earth oxysulfides. Etc. Examples of the constituent material of the rare earth regenerator particles include Nd, Er ₃ Ni, ErNi, HoCu ₂ , Gd ₂ O ₃ , Gd ₂ O ₂ S, and the like.

  The rare earth regenerator particle group has an average particle diameter of 0.01 to 3 mm. When the average particle size is less than 0.01 mm, the gap between the regenerator particles becomes excessively small when the regenerator container is filled, and the air permeability of the working medium gas (He gas) is deteriorated. On the other hand, when the average particle size exceeds 3 mm, the gap between the regenerator particles becomes excessively large, and a sufficient contact surface area with the working medium gas cannot be secured. A more preferable average particle diameter of the regenerator material particle group is in the range of 0.1 to 0.5 mm. Within this range, both the air permeability and the contact surface area of the working medium are improved. The average particle size of the cold storage material particle group is measured with a particle size distribution meter. The particle diameter D of each regenerator particle is determined by (minor axis S + major axis L) / 2.

  In the regenerator material particle group of the present invention, the number ratio of particles having a ratio of the major axis L to the minor axis S of 2 or less is defined as 90% or more. 90% or more of the particles having an aspect ratio (L / S) of 2 or less indicates that the ratio of round particles close to a true sphere is large. If there are many round-shaped particles, the contact between the regenerator particles can be a point contact, so that the contact area between the regenerator particles and the working medium gas can be greatly increased.

  In addition, even if it is a rare earth regenerator material particle having an average particle size of 0.01 to 3 mm, if there are many particles having a large aspect ratio, the gap between the regenerator particles is varied, and the air permeability of the working medium gas is increased. descend. Further, for example, when there are long particles having a large aspect ratio, the contact between the particles is not a point contact but a surface contact portion is increased, so that the contact surface area with the working medium gas is reduced. For this reason, the higher the proportion of particles having an aspect ratio of 2 or less, the more advantageous, preferably 95% or more, and even more preferably 100%.

  Measurement of the ratio of the particles having an aspect ratio (major axis / minor axis) of 2 or less of the regenerator particles is obtained by taking an enlarged photograph of 200 regenerator particles and as shown in FIG. The major axis L and the minor axis S of the material particles are measured, and only the number of particles having an aspect ratio (L / S) of 2 or less is counted and obtained by the following formula.

(Number of particles having an aspect ratio of 2 or less / 200 particles) × 100 (%)
The rare earth regenerator particle group of the present invention has the average particle diameter and aspect ratio as described above, and the number of particles having a concave portion having a length of 1/10 to 1/2 of the circumferential length on the particle surface. The ratio is 30% or more. Here, the circumferential length is the equator length (πD) of the sphere having the particle diameter.

  An example of the regenerator material particle 1 having the recesses 2 and 3 is shown in FIGS. In FIG. 1, a groove-type recess 2 is formed over a length R in the surface portion of the rare earth regenerator material particle 1. In FIG. 2, a hole-shaped recess 3 having a length R is formed on the surface of the rare earth regenerator material particle 1. The shape of the concave portion may be various shapes such as a groove shape and a hole shape. When a plurality of hole-shaped recesses 3 having a length R as shown in FIG. 2 are formed, the total value of the lengths R1, R2,...

  The length R of the recess is defined as 1/10 to 1/2 of the circumferential length (πD) on the particle surface. When the length R of the concave portion is less than 1/10 of the circumferential length, the concave portion is excessively small, and there is almost no effect of increasing the surface area of the cold storage material particles.

  On the other hand, when the length R of the concave portion is excessively large so as to exceed 1/2 of the circumferential length, the concave portion is too large and the structural strength of the cold storage material particles is lowered. When the structural strength is reduced, a problem that the regenerator material particles break due to impact or vibration when the regenerator particles are filled in the regenerator container or the refrigerator is operating is likely to occur. A more preferable range of the length R of the recess is 1/10 to 1/3 of the circumferential length.

  A plurality of the recesses may be formed. However, if the recesses are formed in an excessive amount, the strength of the cold storage material particles decreases, so the number of the recesses per cool storage material particle is two or less, preferably one. Further, as shown in FIG. 1B, even if the number of the recesses 2 is one, if the depth d of the recesses 2 is excessively deep, the strength of the cold storage material particles 1 is reduced. Therefore, it is preferable that the depth d of the recess is 1/10 or less of the diameter (particle diameter D) of the regenerator material particle 1.

  The recess length R is measured by taking an enlarged photograph of each regenerator particle 1 and measuring the diameter D and the recess length R of the particle 1 appearing there. When the regenerator material particles are elliptical, the circumferential length (πD) is obtained with (major axis L + minor axis S) / 2 as diameter D. A method using an enlarged photograph is also effective for the depth d of the recesses 2 and 3. An example of such a method is a method using an AFM microscope.

  In the present invention, the regenerator particles 1 having such recesses 2 and 3 are contained in an amount of 30% or more of the total number. The number of regenerator particles having recesses is measured by taking 200 magnified photographs and measuring the number of regenerator particles having recesses in the photograph (number of regenerator particles having recesses / 200 particles). ) × 100 (%). This operation is carried out three times by selecting different groups of 200 grains, and the average value is taken as the number ratio of the grains having recesses.

  When the number ratio of the regenerator particles having the recesses is less than 30%, the effect of expanding the contact surface area between the regenerator particles and the working medium gas is small. A more preferable range of the number ratio of the regenerator particles having the predetermined recess is 50% or more and 100% or less.

  As described above, the rare earth regenerator particle group in which the number ratio of the regenerator particles having a predetermined recess is adjusted is suitable for a refrigerator used for forming a cryogenic region of 10K or less, and further 4K or less.

  The refrigerator is provided with a cold storage container for filling the cold storage material particles. And the cool storage container with which the said cool storage material particle was filled is mounted in a refrigerator. At this time, it is also possible to make a multistage refrigerator by connecting two or more cool storage containers or providing two or more cool storage material filling regions via a mesh material in the cool storage container. Since this multistage refrigerator is configured in a multistage manner, the regenerator filling region can be increased, and thus the refrigerating capacity can be significantly increased.

  In the refrigerator according to the present invention, the rare earth regenerator particle group of the present invention is filled in a regenerator in a single-stage type. In a multistage refrigerator, at least one regenerator material filling region (cooling stage) is filled with the rare earth regenerator particle group of the present invention. In the case of a multi-stage type, it is preferable to fill all the regenerator material filling regions with the rare earth regenerator particle group of the present invention, but depending on the refrigeration capacity to be obtained, other regenerator materials may be filled with other regenerator materials. Good. Examples of the mesh material include metal mesh materials such as copper and copper alloys.

  The refrigerating capacity of the refrigerator is determined by how efficiently the working medium gas such as He gas and the cold storage material particles are brought into contact with each other. The rare earth regenerator particle group according to the present invention maintains a round particle shape and has a concave portion on the surface thereof, so that the air resistance of working medium gas is deteriorated while maintaining high density filling of the regenerator particles. In addition, the contact surface area between the working medium gas and the regenerator particles can be increased. In particular, it is effective for a type in which the working medium gas reciprocates at a high pressure in the refrigerator, such as a multistage refrigerator.

  Moreover, such a refrigerator is suitable for a refrigerator for operating a superconducting magnet. Superconducting technology is used in magnetic levitation trains and nuclear magnetic resonance apparatuses. In particular, the nuclear magnetic resonance apparatus is widely used such as an MRI apparatus for a human body and an NMR apparatus for a non-human body. It can also be applied to cryopumps used in semiconductor manufacturing equipment. In any case, the improvement of the refrigeration characteristics of the refrigerator leads to the improvement of the reliability and characteristics of the measuring device.

  Next, the manufacturing method of the rare earth regenerator material particle group of this invention is demonstrated. First, as a method for producing the rare earth regenerator material particle group of the present invention, a method of mixing a predetermined amount of a rare earth regenerator material particle having a recess and a rare earth regenerator material particle having no recess.

  Moreover, as a method other than this, the following is shown as a method for efficiently producing the rare earth regenerator particle group of the present invention.

  FIG. 3 shows an example of the manufacturing method. FIG. 3 is a cross-sectional perspective view showing a configuration of a manufacturing apparatus by a rotating disc method (RDP) in which a molten metal is dispersed and solidified by a disc-like rotating body. The manufacturing apparatus includes a cooling chamber 9, a disk-like rotating body 10, a ladle 11, a molten metal 12, a pouring nozzle 13, rare earth regenerator particles (group) 14, and a particle recovery container 15. It is prepared for.

In the rotating disk quenching apparatus using the rotating disk method shown in FIG. 3, first, a molten metal containing a rare earth element and other components as required is prepared in a predetermined amount. The other components are Ni in the case of Er ₃ Ni and Cu in the case of HoCu ₂ . For this reason, the same molten metal as the constituent element of the intended rare earth regenerator material is prepared.

  The molten metal 12 is poured into the ladle 11, and the molten metal 12 is supplied to the disk-shaped rotating body (rotating disk) 10 through the pouring nozzle 13. The molten metal 12 is bounced on the disk-shaped rotating body 10 rotated at a high speed, and rapidly cooled while falling in the cooling chamber 9 to become rare earth regenerator particles 14. The rare earth regenerator material particles 14 fall into the particle recovery container 15 and become a rare earth regenerator material particle group.

  In order to produce cold storage material particles having an average particle diameter of 0.01 to 3 mm, it is preferable to set the diameter of the injection holes provided in the pouring nozzle to 0.05 to 2 mm. Moreover, as for the rotational speed of the disk shaped rotary body 10, 7000-11000 rpm is preferable. The average particle diameter of the rare earth regenerator particles obtained by adjusting the rotational speed and the size of the injection hole (pour nozzle 13) is adjusted.

  When applying the first and second manufacturing methods, the rotational speed of the disk-shaped rotating body 10 is preferably a high-speed rotation of 7000 rpm or more. Further, if the rotational speed is excessively high, regenerator particles having an aspect ratio exceeding 2 are likely to be formed, so the upper limit of the rotational speed is preferably 11000 rpm.

  Moreover, it is preferable that the molten metal 12 repelled by the disk-shaped rotating body 10 is rapidly cooled in an argon atmosphere. If the atmosphere is an argon atmosphere, contamination of impurity gas components (oxygen and nitrogen) can be prevented. If nitrogen is used as the inert gas, it reacts with the molten metal, so nitrogen cannot be used as the cooling chamber atmosphere. For the same reason, atmosphere is not possible.

  The cooling rate of the dispersed metal melt 12 is preferably 10 seconds or less, more preferably 5 seconds or less, from 1000 ° C. to room temperature. In addition, since the temperature of the molten metal 12 changes with materials, initial temperature may exceed 1000 degreeC. The interior of the cooling chamber 9 is preferably coated with a heat resistant resin. If it is resin coating, mixing of impurity metals can be prevented when the rare earth regenerator particles come into contact. Similarly, the interior of the particle collection container 15 is preferably coated with a resin. By preventing the mixing of impurity gas components and impurity metal components, for example, the oxygen content can be reduced to 100 ppm or less, nitrogen to 20 ppm or less, Al to 50 pm or less, and Si to 30 ppm or less.

  The first method for producing a rare earth regenerator material particle group of the present invention supplies molten metal 12 from a pouring nozzle 13 having injection holes having a diameter of 0.05 to 2 mm to a rotating disk rotated at a high speed of 7000 to 11000 pm. To do. The molten granular metal struck by the rotating disk 10 is rapidly cooled. The granular metal melt bounced by the rotating disk 10 rotating at a predetermined rotation speed is vigorously bounced and rapidly cooled while being granular. At this time, the molten metal is rapidly cooled from the repelled traveling direction. Since the inside of the cooling chamber 9 is sealed with an argon atmosphere, the rare earth regenerator material particles 14 are obtained while receiving the air resistance of the argon atmosphere.

  Here, since the granular metal melt is subjected to air resistance, the rear part in the traveling direction of the particles is scattered and rapidly cooled while the argon is involved, and the inclusion of the argon causes the groove-like recess. For this reason, the formation state of the groove-shaped recess 2 can be controlled by adjusting the rotation speed of the rotating disk 10 and the diameter of the pouring nozzle 13 related to the amount of the molten metal 12 introduced. Moreover, when the repelled granular metal melts and cools, the granular metal melts instantaneously collide with each other to form a hole-shaped recess 3 as shown in FIG.

The rotating disk 10 is preferably made of ceramics. Examples of ceramics include alumina (Al ₂ O ₃ ) and boron nitride (BN). When the rotating disk 10 is made of metal, there is a possibility that metal impurities are mixed in the rare earth regenerator material.

  Further, it is preferable that the rotating disk 10 is preheated to a temperature of 800 ° C. or higher and then the molten metal 12 is supplied. If the rotating disk 10 is not warmed, the molten metal 12 and the rotating disk 10 are rapidly cooled when they contact each other, and the molten metal 12 adheres to the rotating disk 10. In order to repel the molten metal 12 smoothly and uniformly, it is preferable to preheat the rotating disk 10 to a temperature of 800 ° C. or higher in advance. In addition, although the upper limit of preheating temperature is not specifically limited, 1000 degreeC is preferable. As shown in FIG. 3, the rotating disk 10 may be provided in the cooling chamber 9. Therefore, if the preheating temperature is excessively high, the inside of the cooling chamber 9 becomes high, and the rapid cooling process of the molten metal 12 becomes insufficient. There is a fear.

  Examples of the preheating method include a method of providing a heater on the rotating disk 10 and a method of preheating the rotating disk 10 by contacting a molten metal 12 that is a raw material for rare earth regenerator particles for a certain period of time. In view of the need for preheating, the rotating disk 10 is preferably made of ceramics.

  The diameter of the rotating disk 10 is preferably in the range of 20 to 100 mm. If the diameter is less than 20 mm, the rotating disk is small. Therefore, if the positioning is not performed accurately when the molten metal 12 is supplied, the molten metal 12 may directly fall without hitting the rotating disk 10. In particular, when the collection container 15 is provided at the bottom of the cooling chamber 9, it is necessary to pay attention because the processed product becomes defective. On the other hand, when the diameter of the rotating disk 10 exceeds 100 mm, when the rotating disk 10 is preheated, the disk retains too much heat, which heats the inside of the cooling chamber 9 and may adversely affect the cooling process. is there.

  FIG. 4 shows another example of the manufacturing method. FIG. 4 is a cross-sectional perspective view showing a configuration example of an apparatus for producing a regenerator material particle group by a rotating nozzle method in which a molten metal is dispersed and solidified by a rotating nozzle having injection holes. The manufacturing apparatus includes a cooling chamber 9, a ladle 11, a molten metal 12, rare earth regenerator material (group) 14, a rotating nozzle 21, and an injection hole 22.

  The preparation of the molten metal is the same as described above.

  A small hole (injection hole) 22 is provided on the side surface of the rotary nozzle 21, and the molten metal 12 is ejected from the injection hole 22 by rotating the rotary nozzle 21 at a high speed. The molten metal 12 jumping out from the injection hole 22 is rapidly cooled while falling in the cooling chamber 9 to become rare earth regenerator particles 14. The rare earth regenerator material particles 14 fall into a particle recovery container (not shown) to form a rare earth regenerator material particle group 14.

  In order to manufacture the regenerator material particles 14 having an average particle diameter of 0.01 to 3 mm, the diameter of the injection holes 22 provided in the rotary nozzle 21 is preferably set to 0.05 to 2 mm. Moreover, the rotational speed of the disk-shaped rotary nozzle 21 is 7000-11000 rpm. By adjusting the rotation speed and the size of the injection hole 22, the average particle size of the obtained rare earth regenerator material particles is controlled. If the rotational speed of the rotary nozzle 21 is excessively high, cold storage material particles having an aspect ratio exceeding 2 are likely to be formed, and therefore the upper limit is preferably 11000 rpm.

  Moreover, it is preferable that the granular metal melt 12 which protrude | jumped out from the injection hole 22 is rapidly cooled in argon atmosphere. If it is in an argon atmosphere, mixing of impurity gas components (oxygen, nitrogen) can be prevented. The cooling rate of the granular metal melt 12 is preferably 10 seconds or less, more preferably 5 seconds or less, from 1000 ° C. to room temperature. In addition, since the temperature of a molten metal changes with materials, initial temperature may exceed 1000 degreeC. The interior of the cooling chamber 9 is preferably coated with a heat resistant resin. If the resin coating is used, it is possible to prevent contamination with impurity metals even when the rare earth regenerator particles come into contact. Similarly, the interior of the particle collection container is preferably coated with a resin. By preventing the mixing of impurity gas components and impurity metal components, for example, the oxygen content can be reduced to 100 ppm or less, nitrogen to 20 ppm or less, Al to 50 pm or less, and Si to 30 ppm or less.

  Even in the case of using a rotary nozzle type quenching apparatus equipped with the rotary nozzle 21 as shown in FIG. 4, it is preferable to preheat the rotary nozzle 21 to a temperature of 800 ° C. or higher in advance. By preheating, it is possible to prevent the molten metal 12 from being cooled more than necessary in the rotary nozzle 21. The upper limit of the preheating temperature of the rotary nozzle 21 is not particularly limited, but 1000 ° C. is preferable. Since the rotary nozzle 21 may be provided in the cooling chamber 9, if the preheating temperature is excessively high, the inside of the cooling chamber 9 may become high temperature and the rapid cooling process may be insufficient.

  In the rotating nozzle method, by providing a large number of injection ports 22 provided on the side surface of the rotating nozzle 21, a larger amount of cold storage material particles can be produced at a time than in the rotating disk method. The diameter of the rotary nozzle 21 is preferably in the range of 10 to 50 cm.

  Moreover, according to the manufacturing method of the cool storage material particle group which concerns on this invention, the particle | grains with a recessed part and the particle | grains which do not have are often mixed. In order to extract only the rare earth regenerator material particles having the recesses from the particle group, a method of sorting by rolling a predetermined inclined surface is effective. Further, when the concave portion is formed on the surface of the particle, the surface friction is slightly reduced, but the roller rolls down at a higher speed than that without the concave portion. It is also possible to sort using this drop speed difference.

  In addition, when it is difficult to apply a rapid solidification method such as rare earth oxide particles or rare earth oxysulfide particles, the surface of the sintered body obtained by the sintering method was polished to obtain predetermined particles. Later, a method of forming necessary concave portions can also be adopted.

[Example]
(Examples 1 to 5, Reference Example 6 and Comparative Example 1)
The molten metal was prepared and Ho and Cu such that the ratio of HoCu _2. Next, by using the rotating disk type quenching device shown in FIG. 3, the molten metal 12 is dropped from the pouring nozzle 13 on the ceramic rotating disk 10 and bounced, so that each example , reference example, and comparative example is performed. Such rare earth regenerator particle group 14 was produced. The rapid cooling operation was performed at a cooling rate that reached 1000 ° C. to room temperature in 5 seconds or less in an argon atmosphere. At this time, the manufacturing process was carried out under the conditions shown in Table 1 for the injection nozzle shape (injection hole diameter), the rotating disk speed, and the like. In addition, a cooling chamber 9 provided with a resin coating was used as the interior.

On the other hand, a comparative example 1 was prepared under the condition that the rotational speed was as low as 2000 rpm.

The average particle diameter of the rare earth regenerator particles produced under the conditions shown in Table 1, the ratio (number ratio) of the regenerator particles having an aspect ratio of 2 or less, 1/10 to 1/2 of the circumferential length on the particle surface The ratio (number ratio) of particles having a concave portion of length was measured. Each parameter was measured by the method described above. The results are shown in Table 2 below.

As is clear from the results shown in Tables 1 and 2, the regenerator material particle group produced using the production method according to this example had a predetermined recess. Further, it was confirmed that the recess shape includes both a groove-shaped recess and a hole-shaped recess. In addition, when preheating temperature was low like the reference example 6, the particle | grains with a large depth of a recessed part were confirmed. Moreover, when the rotational speed was slow as in Comparative Example 1, the ratio of the regenerator particles having an aspect ratio of 2 or less was significantly reduced. Further, in Comparative Example 1, there was little formation of concave portions because there was little argon involved.

(Examples 7 to 11, Reference Example 12 and Comparative Example 2)
The molten metal was prepared Ho and Cu such that the ratio of HoCu _2. Next, using the rotary nozzle type quenching device shown in FIG. 4, the molten metal 12 is poured into the rotary nozzle 21 from the pouring nozzle under the specifications and conditions of the rotary nozzle shown in Table 3, and is placed on the side surface of the rotary nozzle 21. The rare earth regenerator particle group according to each of the examples , the reference examples, and the comparative examples was manufactured by ejecting from a plurality of provided injection holes 22 and quenching with an atmospheric gas. The rapid cooling operation was performed at a cooling rate that reached from 1000 ° C. to room temperature in 5 seconds or less in an argon atmosphere. At this time, the injection hole shape and the rotational speed were set to the conditions shown in Table 3. Further, the interior of the cooling chamber 9 was a resin-coated one.

The average particle diameter of the rare earth regenerator particles produced under the conditions shown in Table 3, the ratio (number ratio) of the regenerator particles having an aspect ratio of 2 or less, 1/10 to 1/2 of the circumferential length on the particle surface The ratio (number ratio) of particles in which concave portions having a length were formed and the ratio of the depth d of the concave portions to the particle size D were measured. Each parameter was measured by the method described above. The results are shown in Table 4.

As is clear from the results shown in Table 4 above, the rare earth regenerator particle group according to each example had a predetermined recess. Further, it was confirmed that the recess shape includes both a groove-shaped recess and a hole-shaped recess. In addition, when preheating temperature was low like the reference example 12, the particle | grains with which the depth of the recessed part became large were confirmed. In addition, when the rotational speed was low as in Comparative Example 2, the ratio of the regenerator particles having an aspect ratio of 2 or less was high, but the formation of recesses was small because of the small amount of argon involved.

  In addition, the proportion of particles having recesses was reduced as compared with the rotating disk method. In the rotating nozzle method, the molten metal is sprayed in a granular form from the injection port, whereas the rotating disk method is a method of playing with a disk rotated at high speed. It is considered that the flipping operation is effective for forming the recess.

(Examples 13 to 17, Reference Example 18, Examples 19 to 23, Reference Example 24, and Comparative Example 3)
The rare earth regenerator particles of Examples 1 to 5, Reference Example 6, Examples 7 to 12, Reference Example 12 and Comparative Example 1 are closely packed in a regenerator (filling rate: about 68%) to produce a GM refrigerator. did.

  Here, the structure of the test GM refrigerator is shown in FIG. As shown in FIG. 5, the GM refrigerator 30 includes outer cylinders 32 and 33 arranged in series in a vacuum chamber 31, a first regenerator 34 disposed in the outer cylinders 32 and 33 so as to reciprocate, and A second regenerator 35, a Cu mesh material 36 filled in the first regenerator 34 as a first regenerator, and a second regenerator particle group according to the present embodiment filled in the second regenerator 35 ( 1c) and a compressor 37 for supplying He gas into the outer cylinder 32.

  Seal rings 38 and 39 are interposed between the outer cylinders 32 and 33 and the first and second regenerators 34 and 35, respectively. A first expansion chamber 40 is formed between the outer cylinder 32 and the first regenerator 34, while a second expansion chamber 41 is formed between the outer cylinder 33 and the second regenerator 35. A first cooling stage 42 and a second cooling stage 43 are formed at the lower ends of the first and second expansion chambers 40 and 41, respectively.

  In addition, in order to measure the characteristics of the regenerator material particle groups prepared in each example and comparative example, a resistance thermometer 44 that measures the temperature of the second cooling stage 43 and a heater 45 that applies a thermal load to the second cooling stage 43 are provided. Attached to the second cooling stage 43.

  A cold storage container having a diameter of 50 mm and a length of 80 mm (a stainless steel tube having a thickness of 1 mm) was used. In each refrigerator, the air permeability of the working medium gas (He gas) and the refrigerating capacity were measured. The results are shown in Table 5. The air permeability is measured by measuring the mass flow rate of working medium gas after supplying a working medium gas with a heat capacity of 25 J / K at a mass flow rate of 3 g / sec and a gas pressure of 16 atm and operating continuously for 500 hours. The value is shown as a relative value when the mass flow rate as air permeability in Example 3 (a refrigerator using the regenerator material of Comparative Example 1) is 100 (reference value). If this value is larger than 100, it is judged that the air permeability is relatively good.

  In addition, when measuring the refrigerating capacity of the regenerator material particle group 1c, the refrigerating capacity is filled with the Cu mesh material 36 in the first regenerator 34, while the second regenerator 35 is filled with the regenerator particle group 1c, and GM. The refrigerator 30 was operated at 60 cycles per minute. The He gas compressed to 20 atm by the compressor 37 is adiabatically expanded repeatedly in the first expansion chamber 40 and the second expansion chamber 41. The generated cold heat is accumulated in the Cu mesh material 36 and the cold storage material 1c, respectively.

The refrigerating capacity in this example was defined as the heat load when the second cooling stage 43 was subjected to a heat load by the heater 45 during operation of the refrigerator and the temperature increase of the second cooling stage 43 stopped at 6K. The results are shown in Table 5.

  As is clear from the results shown in Table 5 above, it was confirmed that the refrigerators according to the respective examples were improved in refrigeration capacity. This is because the contact surface area between the rare earth regenerator material particles and the He gas is increased because the recess is provided. Moreover, although air permeability was inferior in Example 15 and Example 21, this is because the rare earth regenerator material particle group whose average particle diameter is smaller than the comparative example 3 was used.

Moreover, although it confirmed about the failure | damage of the cool storage material particle | grains after 500 hours, damage was not confirmed by the thing which concerns on an Example other than the reference example 18 and the reference example 24, and the thing which concerns on a comparative example, and the intensity | strength of a cool storage material particle is conventional. It was confirmed that it is equal to or better than the product.

On the other hand, in Reference Example 18 and Reference Example 24, some cracks were confirmed in the regenerator particles. For this reason, it was found that the depth of the recess is preferably 1/10 or less of the diameter.

(Examples 25-27 and Comparative Example 4)
Next, a two-stage pulse tube refrigerator was manufactured using the regenerator material shown in Table 5, and the characteristics were similarly measured. The operating conditions of the pulse tube refrigerator were a high pressure He gas pressure of 2.3 MPa and a low pressure He gas pressure of 0.9 MPa. Moreover, the dimension (50 mm in diameter x 100 mm long container (thickness stainless steel pipe | tube)) was used for the dimension of a cool storage container.

  As is clear from the results shown in Table 6 above, both the air permeability and the cooling capacity were improved in the refrigerator using the cold storage material according to each example. Particularly excellent refrigerating performance was obtained in Examples 25 and 26 using the rare earth regenerator particle group according to this example for both the first and second stages.

(Examples 28 to 30)
The same measurement was performed with the rare earth regenerator material particles changed to Nd as Example 28, the Er ₃ Ni changed into Example 29, and the ErNi changed into Example 30. As the manufacturing method, the same rotating disk method as in Example 1 was used. Table 7 shows the diameter of the injection hole of the pouring nozzle, the specification of the rotating disk, and the operating conditions.

The shape of the rare earth regenerator particle group according to each example obtained was measured in the same manner as in the above example. The results are shown in Table 8 below.

The rare earth regenerator particle group according to Examples 28 to 30 as shown in Table 8 above is filled in a regenerator container of a GM refrigerator similar to Example 13, and each refrigerator is assembled. Measurements of air permeability and refrigeration capacity were performed. The results are shown in Table 9 below.

  As is clear from the results shown in Table 9 above, in the refrigerator using the regenerator particle group according to each example, both the air permeability and the cooling capacity were improved. From these results, it was found that the present invention functions effectively even when the material composition is changed.

  According to the rare earth regenerator particle group of the present invention, it is possible to provide a rare earth regenerator particle having an increased contact surface area between a working medium gas such as He gas and the regenerator particle group while maintaining high-density filling. Can do. For this reason, the characteristic of the refrigerator using the said cool storage material particle group, and also the measuring apparatus using the refrigerator can be improved.

  Moreover, according to the method for producing the rare earth regenerator material particle group of the present invention, the rare earth regenerator material particle group of the present invention can be efficiently produced. Moreover, if the rare earth regenerator material particle of this invention is used, a rare earth regenerator particle group can be comprised efficiently.

DESCRIPTION OF SYMBOLS 1 ... Rare earth regenerator material particle 2 ... Groove-shaped recessed part 3 ... Hole-shaped recessed part 9 ... Cooling chamber 10 ... Disc-shaped rotary body 11 ... Ladle 12 ... Molten metal 13 ... Pouring nozzle 14 ... Rare earth regenerator material particle (group)
15 ... Particle recovery container 30 ... GM refrigerator 31 ... Vacuum tank 31
32, 33 ... outer cylinder 34 ... first regenerator 35 ... second regenerator 36 ... Cu mesh material 1c ... second regenerator material particle group 37 ... compressor 38, 39 ... seal ring 40 ... first expansion chamber 40
41 ... second expansion chamber 41
42 ... 1st cooling stage 43 ... 2nd cooling stage 44 ... Resistance thermometer 45 ... Heater

Claims (8)

In the rare earth regenerator material particle group having an average particle diameter of 0.01 to 3 mm, the ratio of the number of particles having a major axis to minor axis ratio of 2 or less is 90% or more, and 1/10 of the circumferential length on the particle surface. number proportion of particles having a recess formed to have a length of ~ 1/2 Ri der least 30%, rare earth cold accumulating material depth of the recess is equal to or less than 1/10 of the particle diameter Particle group. _2. The rare earth regenerator particle group according to claim 1, wherein the rare earth regenerator particle is at least one selected from Nd, Er ₃ Ni, and HoCu ₂ . Refrigerator, characterized by comprising a cold storage container filled with the rare-earth regenerator material particles of claim 1 or claim 2. The refrigerator according to claim 3 , wherein the cold storage container includes two or more stages of cold storage material filling regions via a mesh material. A measuring apparatus comprising a superconducting magnet on which the refrigerator according to claim 3 or 4 is mounted. 6. The measuring apparatus according to claim 5 , wherein the measuring apparatus is at least one of MRI and NMR. In the rare earth regenerator particle having a particle size of 0.01 to 3 mm, the ratio of the major axis to the minor axis is 2 or less, and a concave portion having a length of 1/10 to 1/2 of the circumferential length is formed on the particle surface. Has been
Rare earth regenerator particles characterized in that the depth of the recesses is 1/10 or less of the diameter of the rare earth regenerator particles. The rare earth regenerator material particle according to claim 7 , wherein the rare earth regenerator material particle comprises at least one selected from Nd, Er ₃ Ni, and HoCu ₂ .

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